Forced air circulation hot water heater unit



Oct. 14, J. Y. BARBIER 3,473,006

FORCED AIR CIRCULATION HOT WATER HEATER UNIT Filed Sept. 2, 1966 2 Sheets-Sheeti FIG.3

l 53 f" Q 5Z6 4 7/ 72 3 3 20 53 6 75 INVNENTOR JEAN Y. BARBIER BY E . ATTORNEY Oct. 14, 1969 J- Y. BARBIER 3,473,006

FORCED AIR CIRCULATION HOT WATER HEATER UNIT Filed Sept. 2, 1966 2 Sheets-Sheet /Ar 27 J Z 2712;

FIG.6

THERMOSTAT .45 WWW-- TIME 1 SWITCH THERMOSTAT INVENTOR JEAN Y. BARBIER ATTORNEY United States Patent 3,473,006 FORCED AIR CIRCULATION HOT WATER HEATER UNIT Jean Y. Barbier, St. Louis, Mo., assiguor to Intertherm, Inc., St. Louis, Mo. Filed Sept. 2, 1966, Ser. No. 576,997 Int. Cl. Hb 11/00 US. Cl. 219-365 4 Claims ABSTRACT OF THE DISCLOSURE An electrical unit heater has an elongated liquid heating chamber and a tubular circulation path including a finned elevated portion. The heater is housed in a cabinet having a convection air inlet and a top air outlet. Forced air to augment convection is distributed from an end of the heater through a plenum chamber extending beneath the heating chamber from a blower at said one end. The blower has selectively employable outside air and recirculating air inlets. At least two thermostatically controlled electric heating elements are provided in the heating chamber. For high capacity heating, both elements are energized and convection augmenting forced air is supplied by the blower. The heater can function at lower capacity as a convection heater wherein only one heating element is energized and the blower is inactive. The blower can be used without heating to draw in outside air. The changeover from high capacity to low capacity operation may be controlled by a timer.

The present invention relates to circulating hot water unit heaters energized by electric resistance heating elements, and specifically to the utilization of such unit heaters under conditions of varying demands for heat, air circulation, and introduction of outside air.

Such varying demands exist, for example, in school rooms. The demand for heat may be greatest in the early morning, before the room is occupied; in mid-day there may be no demand for heat but a substantial need for drawing in outside air; and at night the only demand may be for supplying heat at a lower rate. Such varying conditions have not heretofore been met by any unit heater.

The general purpose of the present invention is to meet such needs by improvements in circulating hot water unit heaters using electric resistance heater elements. Specific purposes include providing for operation as a mere convection heater, at a low rate of heat production, or alternately for added heating capacity with the same finned surfaces, by the eflicient use of forced air. Still further purposes include providing for the alternate introduction of outside air or the recirculation of room air, with or without heating, and for attractive and efficient built-in installations beneath windows.

These and other purposes which will be apparent from this specification, are achieved in the present invention, which is generally summarized as follows:

The unit heater has an elongated liquid heating chamber and tubular circulation path including a finned elevated portion, within a preferably built-in, under window cabinet which has a convection air inlet along the wall of the room, and has a top air outlet beneath the window. Forced air is distributed from one end of the heater through a plenum chamber at its underside, extending beneath the heating chamber from a blower at one end. The blower has both an outside air inlet and a recirculating air inlet. Within the heating chamber, at least two electric resistance heating elements extend parallel to each other. Operating at less than full heating capacity, i.e., with only one of said electric resistance heater elements energized, the unit may serve merely as a convecice tion heater. For maximum demand, the other resistance heater element is energized, while air is forced by the blower through a pattern of air ports in the upper surface of the plenum chamber, to utilize the same fins for a greater heat output. The forced air provision in no way interferes with the convection system; to the contrary, it induces an even greater rate of flow through the convection air inlet, thus further increasing the heat output. The blower is also used Without heating, to draw in outside air.

For increased heat transfer efficiency, side-by-side finned tubes are used for the elevated portion of the circulation path. Their combined finned width substantially equals the width of the perforated upper surface of the plenum chamber; and they are fed from the single heating chamber through branched riser and return tube provisions. The specific features mentioned exemplify the present invention, but should not be construed as limiting its scope.

A preferred embodiment of the invention is shown in the accompanying drawings, in which:

FIG. 1 is a perspective view of a unit heater embodying the present invention installed in the wall beneath the window, as shown in phantom lines, the side cover and top grille being partly broken away.

FIG. 2 is a cabinet projection shown in the heater with the top grille and side covering removed. Phantom lines show convection fins.

FIG. 3 is a sectional View taken along line 3--3 of FIG. 2.

FIG. 4 is a sectinonal view taken along line 4-4 of FIG. 2 with the fresh air intake closed, the open position being shown in phantom lines.

FIG. 5 is a fregmentary sectional view taken along line 55 of FIG. 2.

FIG. 6 is an electrical wiring diagram of the present heater.

Referring now to FIG. 1, the present heater is sepecially Well adapted for installations within the walls a of school class rooms, beneath windows b therein, and especially where the wall portion 0 beneath the windows a may be thinned to provide for the recessed installation shown in FIG. 1.

The unit heater illustrated includes an elongated rectangular cabinet generally designated 10 including a top grille panel 11 including louvered openings 12. Left and right ends 13, 14, have inward flanged projecting portions 15, which extend downward to a level above their lower edges. An inner side cover 17 is supported by the inward projecting portions 15, as shown in FIG. 3. It has a lower edge 18, spaced at this level above the bottom of the cabinet. The other sides of the cabinet consist of an outer side plate 19 and a bottom plenum chamber generally designated 20, which extends inwardly from the outer side plate 19 less than the total cabinet width.

The plenum chamber, generally designated 20, extends along the bottom of the cabinet, from the underside of the blower (to be described) to the cabinet right end 14. Considering the cross-section FIG. 3, is is bounded by the lower portion of the outer side plate 19, a metal bottom wall 21, an inward side wall 22 whose height is greater than the spacing of the lower edge 18 above the bottom wall 21, and a top plenum surface 23. The space between the lower edge 18 of the inner side cover 17 and the inward side wall 22 of the plenum chamber 20 serves as an inlet for convection air and induced air flow. 'In FIG. 3 convection air is shown by undulating arrows and induced air by dashed arrows.

Near the left end of the heater, the top plenum surface 23 has a blower scroll opening 24 as shown in FIG. 5. To the right of the blower scroll opening 24 and extending to the right end 14 of the heater, the top plenum surface 23 is perforated by a large number of plenum air flow ports 25 arranged in rows. Between the rows, at intervals along the length of the underside of the top plenum surface 23, are secured transverse bafiles or angles 27. These project downward a small portion of the depth of the plenum chamber, as determined by experiment, sufficiently to convert the velocity of the longitudinally-flowing air into .static pressure at the ports 25, thus to substantially equalize the flow through the air flow ports 25 over the length of the plenum chamber 20. This provision is an effective means to distribute forced air along the entire length of the finned water circulation path of the heater to be described.

Mounted on the upper surface 23, on angles 32 at intervals along its length, is an electrical resistance circulating hot water heater unit generally designated 34.

Within an elongated tubular liquid heating chamber 35,

and held in parallel, longitudinal position by brazed-on end caps 36, are an inner electrical resistance heating element 37 and an outer electric resistance heating element 38. Their mounting in the end caps 36 holds them side by side, spaced apart from each other and somewhat above the bottom of the heating chamber 35. Through electrical connections to its terminal ends 39, hereafter to be described, one of these, for example the inner resistance heater element 37, may be energized independently for convection. By other electrical connectors to its terminal ends 40 the outer heater element 38 may be energized along with the power blower to be described.

Rising upward from the heating chamber 35 and communicating therethrough is a unique water circulation path, which includes a plurality of elongated finned path portions elevated from the heating chamber 35. Referring to FIG. 3, a pair of lower riser tubes 41 branch as in a V-shape upward and to the inner and outer sides, to receive water from the upper portion of the water circulation heating chamber 35. Similar branching left and right end tubular return passage 42, 43 return the water to the left and right ends of the heating chamber 35. At the midpoint of its length, the uppermost level of their slanted portions is the level of support of and flow communication with parallel inner and outer lower finned tube circulation path poritons 44, 45. From this level vertical upper riser portions 47, at the midpoint of the length of each of the parallel path portions 44, 45 and left and right end tubular return passages 48, 49 lead to and from similar inner and outer upper finned tube circulation path portions 50, 51. The direction of circulation of heated water is upward from the central hottest part of the heating chamber 35, through the centrally located, lower riser tubes 41 and upper riser portions 47, thence outward through the finned path portions 44, 45, 50, 51 to and through the return passages 42, 43, 48, 49 to the left and right ends of the heating chamber 35.

The circulation path so described is a more complex version of the central-riser, end-return circulation path described in my co-pending US. Patent application Ser. No. 558,058, filed June 16, 1966, entitled Hot Water Unit Heater Having Improved Circulation Path, now abandoned. Spanning across and above the upper circulation path portion 51 and joining the left and right tubular return passages 48, 49 are inner and outer expansion tubes 52, 53, each having a centrally mounted pressure relief valve 54.

Fins 56 are mounted, as by brazing, along substantially the entire length of the circulation path portions 44, 45, 50 and 51 outwardly of the central riser tubes 41, 47. The fins are preferably rectangular and extend transversely to the tubes, and are of such extent as to nearly fill the width within the cabinet 10. For this purpose, the near edges of the fins 56 on each pair of parallel tubes 44 and 45, 50 and 51, are closely adjacent to 4 each other; while the cabinet 10 is somewhat narrowed above the convection air inlet 18 by the addition of a thick sheet of insulating material 57 to require substantially all the convection air to pass through the fins on the inner lower and upper tubes 44, 50;

The outside air and recirculating air inlet provisions are shown in FIG. 4. Projecting outwardly from the outer side plate 19 for installation through the wall 0 is a rectangular air inlet conduit box 60 equipped at its outer side with several adjacent vertically-pivoted shutterlike damper doors 61, held parallel and controlled from their edges by a common horizontal operator arm 62 moved by a link 63. The air inlet box 60 extends through an opening in the cabinet outer side plate 19, to join an interior air casing 64 on the outer side of (that is, at the inlet of) the blower scroll 30; the casing 64 has along its left side, just inward of the box 60, a recirculation air inlet 65, opened and closed by a similar vertically-pivoted recirculation inlet door 66. The link 63 connects hingedly to one edge of this door 66. At its opposite edge the door 66 is hingedly secured to an electrically controlled driving link 67. In the embodiment shown, the driving link 67 is moved by the driving arm 68 of an air intake control motor 70 which when energized swings the arm 68 angularly in the direction shown by the arrow, to close the recirculating inlet door 66 and open the outside air inlet doors 61. On de-energizing the control motor 70 a tension spring 69, secured to an angle on the housing of the control motor 70, opens the recirculating air door 66 and simultaneously closes the outside air intake doors 61. For the control motor 70, a suitably mounted solenoid or other equivalent actuator may be substituted.

The air casing 64 thus conducts either outside air or recirculating air to the blower scroll 30. In it is mounted a typical centrifugal blower 71 of the squirrel cage type, operated by an electric blower motor 72. At the exit of the scroll 30, a duct portion 73 leads into the blower opening 24 of the plenum chamber 20.

Water is filled into the hot water heater unit 34 above the level of the upper circulation path portions 50, 51 but below the expansion tubes 52, 53. An anti-freeze solution is normally added to the water. The unit is sealed, so as to operate under pressure of air in the expansion tubes 52, 53 when the water expands as it is heated, thus permitting an increase in temperature above the boiling poing at atmospheric pressure. In addition to the pressure relief valve 54, thermostatic limit controls may also be provided, to limit the heating, as is conventional with sealed hot water electric resistance unit heaters used as baseboard heaters.

Th wiring diagram FIG. 6 shows a simple system of electrical controls. Current is introduced through a time switch 74 of the double pole, double throw type, which in FIG. 6 is shown in its day setting position, the night setting being shown in dashed lines. Through its two day setting contacts 75, it supplies current through parallel leads, to the two parallel switch connectors'76, 77 of 'a double pole room thermostat 78. When closed, the connectors 76, 77 carry current in parallel through the inner side resistance heater element 37 and the outer side element 38. Through the day setting contact 75 current is also supplied in parallel to the blower motor 72 and a fourth parallel lead including the air intake control motor 70 and an intake single pole control thermostat 79 in series.

The double pole room thermostat 78 closes on drop of temperature below a desired setting of say 75 F. The single pole air intake control thermostat opens on drop of temperature below say 70 F. to de-energize the control motor 70 and hence close off the outside air doors 61 when the room temperature falls below such 70 F. setting.

During the night setting of the time switch 74, shown in dashed lines, the night setting contact 80 conducts current in series to the inner resistance heater element 37 through a night thermostat 81, which closes on temperature drop to a temperature of say 40 F. This minimizes the cost of night operation of the heating system. Energizing only one of the two heater elements 37, 38 without any forced air from the blower 72, permits efficient use of the entire finned circulation path portions 45, 46, 50, 51 by convection. Heating by one heater element only draws in convection air through the convection air inlet provided between the lower edge 18 of the inner side cover and the inward side wall 22 of the plenum chamber 20. The insulating material 57 tends to divert the air toward the center of the cabinet. The unique branched riser and return tube construction provides in effect separate inner and outer side water circulation paths from the common heating chamber 35, the flow velocity in each being a function of the actual heat exchange rates. Hence whether or not the convection air flows evenly throughout the entire inside of the cabinet is not critical; in any event, close spacing of the fins 56 on the inner and outer circulation path portions as described, adjacent to each other and to the cabinet side walls, tends to assure good air distribution.

When the time switch 74 is at its day setting, as in the circuit illustrated in FIG. 6, the blower motor 72 will be in constant operation, directing forced air through the ports 25 of the plenum chamber 20 and thus causing a rapid flow of air upward through the adjacent fins 56. Since the combined finned width of the adjacent fins 56 on the side-by-side lower path portions 45, 46 and upper path portions 50, 51 substantially fills the available inner width of the cabinet (and coincides with the width of the perforated top wall 23 of the plenum chamber 20) there is excellent efficiency of heat transfer to the rapidly flowing air suflicient to carry away the heat supplied 'by both simultaneously-energized heater elements 37, 38.

So long as there is heating, there will also be convection air in-fiow through the convection slot, between the lower edge 18 of the inner side cover 17 and the plenum chamber 20. However, wherever the blower operates (regardless whether either or both heaters are energized) inflow through this slot will be increased by augmentation. The more rapid flow of air upward from the plenum chamber 20 induces the air entering through the convection slot to increase its velocity. By such flow augmentation the heating efiiciency of the apparatus is increased. The augmentation eifect also aids in the recirculation of room air when there is no demand for heat; for the recirculation inlet door 66 itself will be closed while the blower 72 is drawing in outside air through the open air intake door 61.

Many vraiations in the apparatus are feasible, depending upon the precise mode of operation desired. The embodiment described includes certain specific engineering choices made for an illustrative installation, for example, the wiring arrangements and the linkages. Such specific details of structure and mechanisms will be recognized as matters of choice, to be readily varied by persons skilled in the art. Accordingly this invention is not to be construed narrowly, but rather as coextensive with the claims.

'I claim:

1. For use alternately as a convection heater or with forced air circulation,

an electric resistance circulating hot water unit heater having an elongated liquid heating chamber,

a tubular circulation path communicating through the heating chamber and including a similarly elongated finned convection path portion elevated therefrom,

a plurality of electric resistance heating elements extending parallel to each other within said heating chamber and substantially throughout its length,

a cabinet enclosing said unit heater and having at its lower portion a convection air inlet and having at its upper portion an air outlet,

whereby to permit the flow of air into the cabinet through the convection air inlet and thence through the finned path and air outlet,

said cabinet further having means to distribute forced air along the length of the finned path portion and a duct inlet to said forced air distribution means,

an electric-powered blower associated with said duct inlet, together with electric circuit-making means to energize one of said resistance heater elements independently of the blower, and

further electric circuit-making means to simultaneously energize the blower and a second of said resistance heater elements,

whereby to add forced air circulation through the distribution means and finned convection path portion and in so doing to augment the air flow to the finned path portion through the convection air inlet.

2. A hot water unit heater as defined in claim 1,

the convection air inlet being along the lower edge of one side of the cabinet,

the forced air distribution means being a plenum chamber extending longitudinally along the bottom of the cabinet laterally adjacent to the air convection inlet,

the duct inlet thereto being at one end of said plenum chamber,

said plenum chamber having air flow port means in its upper surface and means adjacent to the port means to substantially equalize the flow therethrough over the entire length of the plenum chamber.

3. The 'hot water unit heater defined in claim 1,

the blower having a casing including an outside air inlet means and a recirculation air inlet means,

together with means to automatically close one of said air inlet means as the other is opened.

4. The hot water unit heater defined in claim 3,

the said further electric circuit-making means including means to energize the blower independently of said resistance heater elements,

whereby the unit may serve to draw in fresh air without heating.

References Cited UNITED STATES PATENTS 1,983,437 12/1934 Carr 2l9--341 2,122,168 6/1938 Woolley -123 2,244,172 6/1941 Novak 219-365 2,360,071 10/1944 Noll 219365 X 2,820,880 1/1958 Huntsinger 219-364 X 2,876,690 3/ 1959 Pierce 165-55 X 2,894,108 7/1959 Brand et a1. 219-365 X 2,988,626 6/ 1961 Buttner 219-364 X ANTHONY BARTIS, Primary Examiner US. Cl. X.R. 

